A Masked Diboron in Cu-catalysed Borylation Reaction: Highly Regioselective Formal Hydroboration of Alkynes for Synthesis of Branched Alkenylborons

The use of a masked diboron as a boron source in the presence of a Cu-N-heterocyclic carbene (NHC) catalyst enables alkyl-, aryl-, heteroatom- and silyl-substituted terminal alkynes to undergo α-selective formal hydroboration to give diverse branched alkenylboron compounds exclusively. Synthetic potential of this α-selective hydroboration has been demonstrated by total synthesis of pharmaceutically significant bexarotene and LG100268.